As mentioned in the introduction, I started with a Rancilio Silvia / Rocky combo and upgraded to La Valentina / Mazzer Mini. Consistency with Silvia was more of a challenge than it is with Valentina. Except for the cool down flush, making espressos and cappuccinos is pretty much hassle-free. Valentina produces very good results day after day—convincing me that the consistency and temperature stability of the E61 design is indeed as good as I'd heard. Despite all the hullabaloo about electronic temperature controls you may read about for some espresso machines (often referred to as “PID'd espresso machines”), it is not difficult to consistently obtain nearly one-degree accuracy during an extraction with a modest amount of practice. If you're not convinced, I invite you to read on.

How I Learned to Love HXs (Summary)

The how-to How I Stopped Worrying and Learned to Love HXs covers temperature management for heat exchanger espresso machines in detail, including charts showing the in-basket brew temperature during an extraction. OK, OK, perhaps that is too much detail for some readers! If you have already read the article, skip to the next section. Otherwise, allow me to summarize it, beginning with a few terms:

• recovery time - interval between consecutive shots for the group to reheat to brew temperature (about two minutes).
• rebound time - pause after flushing but before beginning the extraction (usually between 15-25 seconds).
• water dance - hissing and sputtering during the cooling flush; the water settles down around 206°F.

The rebound time affects mostly the first third of the shot, producing what I call the HX hump, which is the momentary rise above the target brew temperature. Lowering the boiler pressurestat setting increases the rebound time (e.g., rebound time is approximately 25 seconds at 0.9 bar and 15 seconds at 1.1 bar). The flush amount affects the overall brew temperature.

Does this sound overly technical? Well fortunately there's an easy-to-remember guideline you can use until you've developed an intuitive feel for the correct timing. Quite simply, the temperature drops approximately one degree per second during the cooling flush after the water dance stops.

To warm up the portafilter prior to an extraction, I prefer to start the grinder and then remove the portafilter halfway through the flush, which gives me about 40 seconds to fill and tamp. Despite my noting specific times in seconds, to be honest, I haven't bothered with timers or measuring the flush amount once I developed a good feel for when it's going redline; you too will get the hang of it after a few weeks with Valentina.

Why the E61 Design is So Popular

The E61 group has a well-deserved reputation for being a “forgiving” design. Part of this forgiveness is due to the impressive temperature stability discussed earlier and graphically demonstrated by the last two-thirds of the temperature profile above. There is a slight difference between the shapes of La Valentina and La Marzocco's temperature curves and it does have a minor effect on the in-cup result. If you are the type of home barista that enjoys experimentation, you can “work” a blend's flavor characteristics by manipulating the rebound time as documented in HX cooling flush in detail. On the other hand, if you're the keep-it-simple type, following the shorthand guidelines in the previous section will produce very good results easily.

Another characteristic contributing to the E61's forgiving nature is its initially slow rise in brew pressure, known as progressive preinfusion. The slow increase in pressure allows the coffee puck extra precious seconds to expand, thereby closing micro-fissures that could otherwise lead to channeling. You can also see another effect of this deferred pressure rise in the temperature profiles above—Valentina's temperature increases more slowly because the brew chamber fills gradually during preinfusion. Also note that the E61's initial temperature starts higher (around 185°F). The E61's thermosyphon circulates water more aggressively from the heat exchanger towards the grouphead compared to commercial groups, resulting in a higher starting temperature.

All technical minutia aside for a moment, the happy consequence of the E61 design is that Valentina will produce a reasonable extraction even if the amount of coffee, tamp, or grind are less than ideal (however, if you do run into problems, look to the Extraction Troubleshooting Checklist for suggestions on correcting them).

Pulling Shots by the Numbers

Below are the steps for making your first espressos. Let's assume that you've adjusted your grinder for a reasonable 25-27 second extraction:

• Allow La Valentina at least 25 minutes to warm up.

  An accurate and stable brew temperature relies on the entire brew pathway being up to temperature. If you prefer not to leave La Valentina on 24/7 and you're rushed in the morning, consider a timer to preheat the machine before you wake.

• Start the grinder and press the brew button to begin the cooling flush. Remove the portafilter after about 10 seconds, dry out the basket, and then fill and tamp firmly.

  Generally I measure by volume, but sometimes use a precision scale to weigh out the beans and run the grinder until empty. I found that 17.5 grams of coffee beans / a small heaping basket full of grinds worked best (a level basket holds around 16 grams before any settling). Smooth out the grinds to an even bed of coffee as described in Dose, Distribute, Tamp. Repeat.

  It is important to have some clearance between the dispersion screen and the top of the puck. This facilitates the even distribution of water over the surface and allows the puck to expand upward to meet the dispersion screen as it absorbs water. You can quickly double-check clearance by gently placing a nickel on the top of the puck, drying the dispersion screen, then locking in and removing the portafilter. The puck should only show a faint impression of the coin if the clearance is correct.

  The rebound time after the cooling flush is less than one-half minute at a pressurestat setting of 1.1 bar. If you remove the portafilter about halfway through the flush and start to prepare the basket, that doesn't leave a lot of time to dose, distribute, and tamp before you should start the extraction. Alternatively, if you prefer to keep the portafilter in the group for the maximum time and work at a gentler pace, try removing the retention clip from the portafilter so the basket drops in and removes easily. Then you can tamp at your leisure while the portafilter remains in the grouphead. Once the basket and coffee are ready, a quick turn to remove the portafilter, flush, drop in the basket, then back in the grouphead.

  Hint: Listen for the hissing of steam and gurgling of boiling water before locking in the portafilter. Continue drawing water for about five seconds after the stream has settled down, for around six ounces total. Depending on the blend and your taste preference, the recovery time after the cooling flush is somewhere between 15 seconds (puck surface temperature briefly peaks about one or two degrees Farenheit above target brew temperature) to 35 seconds (puck surface temperature peaks around four degrees above brew temperature).

• Lock in the portafilter and toggle the brew button to start the extraction.

  Take a moment to rinse the grouphead by loosely locking in your second portafilter with backflush disk and running the pump while slowly jiggling the portafilter handle back and forth. This “wiggle-rinse” will wash most of the loose grinds off the grouphead and dispersion screen and over the sides of the portafilter into the driptray. Be careful not to splash yourself and watch for hot water running down the portafilter handle!

  Remember to relock the portafilter back into the grouphead to keep it warm.

At the end of a session, I also recommend a quick water backflush to clear the pathway from the grouphead to the pressure relief valve that empties into the back of the driptray. Refer to Espresso Machine Cleaning - Why, How, and When for more details on a cleaning regime that applies well to La Valentina.

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